In the pre-Zero Hour
Legion, Cosmic Boy was romantically involved with Night Girl (Lydda Jath)
from the Legion of Substitute
Heroes. During the "Five Year Gap" following the
Magic Wars, he lost his powers in the course of a war between the
planets of Braal and Imsk (the
homeworld of Shrinking Violet), in which the Imskian
army used a "dampener" on the magnetic fields within the Braalian
soldiers. "Vi" was on the scene when her fellow Legionnaire was
crippled by the dampener during the battle of Venado Bay, and
harbored deep guilt for years. Now going by plain old "Rokk Krinn",
Rokk retired to the slums of a demilitarized Braal with his wife
Lydda, who gave birth to their son "Pol" (named for Rokk's
brother). When Reep Daggle reformed the Legion, a
powerless Rokk joined up, moving his family to the Legion's new
headquarters. The former "Cosmic Boy" continued to serve with honor
during the adult Legion's tour of duty, proving that he needed no
powers to be a hero. Rokk did however regain his powers shortly
before Zero Hour, thanks to a special
pair of power gauntlets. He took on the codename "Polestar", only
to renounce the power gauntlets after they began to affect his
mind. After learning that he was apparently destined to become the
Time Trapper, Rokk
and the rest of the Legion were erased from history by Zero Hour.

Post-Zero
Hour

In the post-Zero Hour Legion, Rokk Krinn came from a poor family
but became a superstar in the Braallian sport of Magnoball, earning
the nickname "Cosmic Boy" after winning the Magnoball Cosmic Games.
He sent most of his earnings to his family, unaware that his
manager, Alex Cuspin, was embezzling them instead. After being
approached by R.J. Brande to form the Legion, Saturn Girl discovered
and revealed the truth about Cuspin. Rokk promptly dismissed his
manager and had him arrested. The founding members voted him
leader, but soon after found out that Leviathan, a Science Police veteran, had been
appointed to leadership by the United Planets President. Leviathan
would shortly thereafter give Cosmic Boy the leadership position
after the death of Kid
Quantum, a position he served in very admirably.[1]
After the attack on Earth by the White TriangleDaxamites, he seemed to turn into a controlling
marionette under the thumb of UP President Chu. During this period,
he made many unpopular decisions, including forcing his best friend
Garth Ranzz and Ultra Boy off the team.
However, this was a ruse planned by himself and Invisible Kid to
expose the corruption of the UP President.

After this, he voluntarily stepped down from leadership, feeling
that he had served as leader for long enough. When Shrinking Violet
fell under the influence of the Emerald Eye of Ekron, Rokk was one of
the team members the Eye sent to the 21st Century. During this
period, he and Saturn Girl began a relationship, but was then
rendered comatose during a battle with Doctor Psycho. While he apparently
recovered, it was later revealed that Saturn Girl had been
subconsciously manipulating his comatose body since Psycho's
attack. She also realized that she was in love with Garth. The
relationship ended, but the two remained close friends. After
returning to the 31st Century, he would deal with an attempt on his
life by his former manager, who had been released from prison.
After half the team was lost in a rift in space, the Legion was
disbanded by Leland McCauley, who had become the
president of the United Planets. Brande quickly recruited him to
reform the Legion in secret and Rokk again led the team for a short
time, discovering that McCauley had been killed and was being
impersonated by Ra's
al Ghul. After defeating Ra's, Rokk would step down from
leadership again. Later, he began a relationship with the Legion's
new leader, Kid
Quantum II.

"Threeboot" Continuity

In Legion of Super-Heroes (vol. 5) #1, Cosmic Boy is
the leader of the Legion of Super-Heroes. After seemingly
destroying the Dominators homeworld (he actually sends it
to the Phantom
Zone), Cosmic Boy is voted out of office, being replaced by Supergirl. He then joins a
superhero team from the 41st century, who come back in time to
offer him membership.

Cosmic Boy is like the
all-around leader who puts it all on his shoulders, but he's
magnetic. His powers are all about magnetics, and so it carries
over to his personality. An he struggles to bring all the Legion
back together. He's like, 'We can do this" We can bring it
together' It comes naturally to him.

Cosmic Boy was featured in a four-part limited series, cover
dated December 1986 through March 1987. A tie-in to the Legends
limited series, it was written by Paul Levitz, with art by Keith Giffen, Ernie Colón, and
Bob Smith.

In the series, Cosmic Boy and Night Girl have travelled from the
30th century to enjoy a vacation in the 20th century. They find
themselves threatened by many citizens and residents of the United
States, who have been manipulated by Glorious Godfrey as part of a scheme
by Darkseid to discredit
Earth's superhero community.[3] Soon
after arriving, Cosmic Boy encounters Superman, who does not recognize him -- even
though Superboy was a member of the Legion
for years. He and Night Girl review videotapes of recent history,
including references to the bombing of
Hiroshima, the explosion of the American
space shuttle Challenger, and the meltdown at
the Chernobyl nuclear power plant, but no mention of Superman's
early career as Superboy. Cosmic Boy, a 20th century Earth history
buff, insists that none of these events are correct. As theirs is
one of the first journeys through time since the Crisis, the couple fears that
some is terribly wrong with history. The future could be in serious
danger, since many of the worlds in the United Planets were colonized by
settlers from Earth. A space shuttle mission carrying a satellite
crucial to Earth’s future development of space travel goes awry,
with the shuttle exploding. Cosmic Boy magnetically catches the
payload and sends the debris harmlessly toward the ocean, but
American soldiers assume that he is a foreign spy. They attack him,
implementing President Ronald Reagan's directive outlawing all
superhero activity.

Seeking to protect to the satellite, Cosmic Boy and Night Girl
travel to NASA facilities in
Houston where they meet Jason, one of the astronauts who designed
the shuttle. They help to quell a riot that break out when
demonstrators break down the gates at NASA, and Cosmic Boy becomes
convinced that some unseen enemy is deliberately trying to prevent
the mission. As they depart, the couple notes that both of their
families are from worlds settled during the Great Emigration from
Earth. They are unaware that the last name of Jason -- the
astronaut they just met -- is Krinnski . . . which implies that he
may be a distant ancestor of Cosmic Boy, whose real name is Rokk
Krinn.

Cosmic Boy and Night Girl decide to return to the 30th century,
where time travel experts Brainiac 5 and Circadia Senius might be able
to determine the problem. Upon entering the timestream, their Time
Bubble encounters a storm and starts to shake violently. They are
forced to return to the 20th century. They turn to Jason Krinnski
for assistance, who does his best to help them repair the Time
Bubble. However, their second attempt to leave fails, as if there
was a barrier blocking them. Realizing that they need a massive
power source to propel the Bubble all the way to the 30th century,
Cosmic Boy harness the electromagnetic energy from Earth's magnetic
field. They breached the barrier, but are propelled past their own
century, all the way to the End of Time, where they are confronted
by one of the Legion’s deadliest enemies: the Time Trapper.

The Trapper toys with the couple, giving them an hour to find
their way back to the 30th century. They eventually make their way
through the Trapper's Citadel to their Time Bubble, just as the
last grains in the hourglass are about to fall. Cosmic Boy uses his
power to warp the hourglass, closing it so that the last grain will
never fall. Amused, the Trapper allows them to leave. He directs
the Time Bubble to the 30th century, placing it right in front of
Legion Headquarters. However, he warns the couple that this will be
their final journey through time, and that "the next occasion when
a Legionnaire dares break the time barrier will be the last." As
the two of them race to warn the Legion about what has occurred,
the Trapper realizes that the Legionnaires will be returning for
him. He finds this quite satisfying, as he looks at a pair of
statues of Superboy and his dog Krypto.

Costume

Cosmic Boy's original costume was pink with black at the sides,
with four white circles, the code-name "Cosmic Boy" written on the
chest, and a plastic bubble space helmet. After his first
appearance, the helmet and the codename were replaced with white
epaulets. For a period in the late 1970s, he was portrayed in a
costume that was essentially a black bustier with black gloves and boots, with bare arms, shoulders, chest and legs.
This costume – one of several designed by Mike Grell – received a mixed reaction from
fans, some of whom felt it inappropriately sexualized Cosmic Boy,
while others saw it as innovative and reflective of the times in
which the comic was then being published. Cosmic Boy returned to a
close variation on the original costume a few years later. As
Polestar, he wore a black and purple bodysuit with a stripe up the
side and a black cowl. In the post-Zero Hour Legion, he wore a
version of his original costume with lavender as the primary color
instead of pink. On this version of the costume, the four circles
on the chest were actually discs that he could magnetically
manipulate and use as weapons. The "Threeboot" version is a similar
pattern, with blue as the primary color and black circles instead
of white.

Legion of Super
Heroes

Cosmic Boy was a recurring member of the animated series, Legion of
Super-Heroes. It reveals that he was the original leader
of the Legion. He is vocally played by Wil Wheaton.

It appears that he has some romantic feelings for Saturn Girl in
the season 1 episode "Chain of Command". He wanted (or ordered)
Saturn Girl to stay with him and Brainiac 5 where she'll be safe. Saturn Girl
angrily objected that she was able to take care of herself. She
flies off to help the rest of the teammates before Cosmic Boy tried
to apologize. Whether or not they resolved following the mission
was never addressed.

He loses an election for leadership position to Bouncing Boy,
but seems to have regained his position at the beginning of season
2.

Smallville

Ryan Kennedy as Rokk/Cosmic Boy on Smallville.

Cosmic Boy, along with Saturn Girl and Lightning Lad, made
his live-action debut in the eleventh episode of the CW's series
Smallville
(eighth season) portrayed by actor Ryan Kennedy. In the episode,
Rokk is seen as the silent leader type. The most determined of the
group, Rokk comes the closest to killing Chloe Sullivan, only to be stopped by
Clark Kent. When the group does defeat Brainiac without the use of murder, Rokk
changes the Legion rules accordingly. Just before he leaves, Rokk
warns Clark of the days ahead, telling him to be careful. Though
mainly referred to as Rokk, Lightning Lad calls him "Cos" at one
point in the episode.

He later returns in the season finale to give Clark a new Legion
ring after his was destroyed in "Infamous" and warn him that
nothing can stop Doomsday from killing him. He gives
Clark the ring and tells him to send Doomsday to the future, as the
Legion is prepared to fight him there.[4]